1. Field of the Invention
The subject disclosure relates to a vascular introducer assembly, and more particularly, to a vascular introducer assembly that includes a dilator, a sheath for accommodating the dilator, a locking mechanism for temporarily securing the dilator and the sheath to one another and an adjustable hemostatic seal for limiting fluid egress from the introducer assembly.
2. Background of the Related Art
The percutaneous introduction of diagnostic and/or therapeutic devices such as pacemaker leads and cardiovascular catheters into a blood vessel is typically accomplished with the aid of an introducer assembly. Introducer assemblies generally include a dilator having a tapered end portion and a thin-walled introducer sheath having a lumen extending therethrough to initially accommodate the dilator, and subsequently accommodate the passage of a pacemaker lead or catheter therethrough. Typically, the percutaneous introduction of an introducer assembly is accomplished by first inserting a needle into the blood vessel at a desired location and its position is verified by observing fluid return or by a similar method. While the needle is held firmly in place, a guidewire is inserted through the needle cannula to the desired depth. The guidewire is then held in place and the needle is withdrawn. Pressure is applied on the puncture site in order to minimize blood loss. Next, the introducer assembly is threaded over the guide wire. The introducer assembly is grasped close to the skin surface and advanced through the tissue to the desired position. Then, the dilator and guidewire are removed, leaving the sheath installed. A lead, catheter or similar diagnostic or therapeutic device is then introduced into the sheath and advanced to the desired position. Lastly, the sheath is removed, leaving the device disposed within the blood vessel of the patient.
It is known to configure an introducer sheath in such a manner so that it may be easily removed or separated from the lead or catheter after it has been emplaced. For example, it is known to provide score lines in the wall of the sheath to enable the sheath to be pealed away, slit or split open. Once the sheath is removed and catheter is emplaced, therapeutic medical devices such as endocardial pacing/defibrillation leads may he introduced into the blood vessel through the catheter.
Occasionally, the dilator slides out of the sheath during the insertion of the introducer assembly into a blood vessel. This significantly complicates the insertion procedure because the introducer assembly may not slide smoothly into the blood vessel and the insertion may not be effective. In some instances, when the dilator slides out of the sheath during insertion, the sheath may proceed completely through the vein, and break, bend, or tear. Also, if the dilator separates from the central lumen of the sheath, blood may flow undesirably from the vessel through the sheath.
In addition, once the sheath is inserted into a blood vessel, it provides a passage for the free flow of blood. This may result in significant blood loss to the patient. The sheath also provides an open passage for the introduction of air into the vein. This could cause an embolism in the venous system of the patient. To overcome these problems, vascular introducers have been developed with hemostatic valves that prevent the free flow of blood through the introducer sheath.
Examples of such prior art devices are disclosed in U.S. Pat. No. 5,124,904 to Lee and U.S. Pat. No. 5,409,463 to Thomas et al., the disclosures of which are incorporated herein by reference in their entireties. In each of these devices, the hemostatic valve is configured in such a manner so that it creates frictional resistance to the passage of therapeutic devices such as flexible cardiac leads. This makes introduction of the lead difficult and can actually cause damage to the lead.
It would be beneficial therefore, to provide a vascular introducer having a sheath with a hemostatic seal that may be selectively, radially adjusted to accommodate frictionless, unobstructed passage of a diagnostic or therapeutic device therethrough.
Furthermore, there is a need for a vascular introducer assembly that provides a mechanism for securely locking the dilator and sheath together during insertion of the introducer assembly to prevent axial movement of the dilator relative to the sheath.